It has been found that high frequency circuits "leak" RF energy. The FCC has required that this leakage be kept below certain standards. Since the FCC made requirements put rules in place aimed to prevent the leakage, radio frequency circuits are typically enclosed in a metal container. When the enclosure cover is off while the circuits are being optimized in their performance, the RF energy escapes to the outside. It has been found that when a cover is placed on the enclosure, and the RF energy can no longer escape to the atmosphere, that it may be reflected to sensitive portions of the circuit in a positive feedback manner, and conversely may cause oscillations or other detrimental effects. Thus, it is important in high gain circuits that some type of RF energy absorption material be used to minimize reflective energy. The use of RF energy absorber blocks adjacent such energy emitting circuitry is one such solution to minimize reflective energy.
When a high gain amplifier capable of passing high frequency radio signals is placed in an enclosed environment, standing waves of other detrimental effects are sometimes initiated such that the amplifier will oscillate. Thus, while the amplitude/frequency response of the circuit may be satisfactory after adjustment of various parameters with the cover of the enclsure off, the amplifier may break into oscillation upon complete enclosure of a circuit by fastening down the cover. RF energy absorber blocks can be positioned adjacent the RF circuitry to minimize adverse results upon encosing the RF circuitry.
In the past, the absorber blocks have been held in place by various means such as a screw-type rod with nuts used to hold the absorber blocks in place against the wall until the optimum placement is determined. Upon proper placement, the absorber blocks are often epoxied or otherwise permanently attached to the walls. If the screw rod is made of metal, as has been the case in the past, and the parts accidentally fall onto the microwave circuit during the positioning process, the adjacent microwave circuitry can be damaged mechanically and/or electrically.
The present invention improves upon the prior art referenced above by making the retainer device out of a low dielectric material such as nylon or delrin. If the metal screw were merely made out of one of these materials, the potential for damage from dropping it would be minimized both electrically and mechanically. However, the screw-type device is still awkward to install and to adjust for block re-positioning purposes.
The present concept uses deformation of a portion of a retaining device to provide sufficient forces between the absorber blocks and the walls to hold these blocks in position long enough to accurately ascertain block position for optimum circuit performance characteristics. Properly positioned blocks can then be epoxied or otherwise adhesively attached to the walls. While the present retaining device could be removed at this time, it is typically left in place for potential future use if the circuit board needs replacing in the field.
It is an object of the present invention to provide an improved absorber block retainer.